Mathew Boulton was the business partner of James Watt. He had a manufacturing firm in which James Watt was the partner. Together, they manufactured steam engines. In the late 18th century, their firm, Boulton and Watt, installed hundreds of steam engines across Britain thereby contributing to the mechanization of the British economy.
Even though Watt was the inventor of the steam engine, Boulton is considered important because without him, Watt could not have obtained the funding and the organisation to manufacture steam engines on a large scale.